The most difficult Mars riddles

Sojourner was the first Mars rover. It was much smaller than Curiosity, whose wheel is about the size of the whole Sojourner. It landed on July 4, 1997 as part of the Mars Pathfinder mission on Mars's Ares Vallis and remained in contact with Earth till September 27, 1997.

The Martian year is almost twice longer than Earth's year.

Viking 1 was the first of two spacecraft (along with Viking 2) sent to Mars as part of NASA's Viking program. On July 20, 1976, it became the first spacecraft to land successfully on Mars and perform its mission. Viking 1 held the record for the longest Mars surface mission of 2307 days until that record was broken by Opportunity on May 19, 2010.

The only efficient protection against high energetic cosmic radiation, one we are granted with, is Earth's magnetic field. Both during a long flight to Mars and through the stay on the planet, that did not form electromagnetic field, astronauts would be exposed to ionization.

The solar day on Mars is only slightly longer than an Earth day: 24 hours, 39 minutes, and 35.244 seconds.

Olympus Mons (Latin for Mount Olympus) is a large shield volcano on the planet Mars, having a height of nearly 22 km (14 mi). Being a shield volcano, it has a very low profile. The average slope on the volcano's flanks is only 5°. Because of that, an observer standing on the Martian surface would be unable to view the entire profile of the volcano, even from a great distance.

Mars is the fourth planet from the sun. Mars has two Moons, Phobos and Deimos. They were both discovered in 1877, by Asaph Hall at the Naval Observatory in Washington DC.